Triazole treatment of explant source provides stress tolerance in progeny of Geranium (Pelargonium hortorum Bailey) plants regenerated by somatic embryogenesis

The hypothesis that chemically induced stress tolerance in plants can be transferred to a larger clonal population regenerated by somatic embryogenesis was evaluated using the triazole compound paclobutrazol as a chemical inducer of stress tolerance in Geranium (Pelargonium horturum Bailey). Seeds were imbibed in 3.4, 10.2 or 17.0 muM (1, 3, 5 mg L-1) paclobutrazol for 24 h and germinated for 7 days. Hypocotyl explants were cultured in vitro to induce somatic embryogenesis. Plants regenerated from somatic embryos were exposed to heat stress at 56 degreesC. Explants treated with 3.4 muM paclobutrazol yielded a substantially higher number of somatic embryos compared with untreated explants. In contrast, 17.0 muM paclobutrazol treatment inhibited embryogenesis producing a significantly lower number of somatic embryos. There was no difference in the embryo number between control and 10.2 muM treatment. Somatic embryos derived from 3.4 and 10.2 muM paclobutrazol treated explants developed into plants at a faster rate than the control and 17.0 muM treatments. Plants derived from paclobutrazol-treated explants displayed a greater tolerance to heat stress compared with the controls. Observations in this study provide a technique for regenerating plants in tissue/cell culture with additional desirable traits such as stress tolerance with minimal chemical contamination of the environment.